A conventional electroconductive contact unit for use in contact probes for electrically testing conductor patterns of printed circuit boards and electronic devices typically comprises an electroconductive needle member and a tubular holder that receives the needle member in an axially moveable manner, and the needle member is resiliently urged by a coil spring in the direction to project the tip of the needle member from the front end of the holder so that the tip of the needle member may be resiliently brought into contact with an object to be tested.
Silicon wafers and ceramic packages for use with semiconductor devices and glass panels for use in LCD panels are made of materials having a relatively high hardness. These components are provided with electric circuitry, and are subjected to electric testing during the manufacturing process. An electroconductive contact unit (contact probe) is used for such a purpose, and is adapted to establish electric contact with a part of the circuitry such as a terminal.
When the object to be tested consists of a component made of a hard material such as those mentioned earlier, and the contact probe uses needle members made of conventional SK material (carbon tool steel), repeated use of the needle members will result in the wear and deformation of the contact points in time. As a result, a stable contact resistance may eventually become impossible. Therefore, the needle members are required to be replaced in a relatively short period of time, and this increases the running cost.